Abstract
One of the main objectives of watermarking is to achieve a better tradeoff between robustness and high visual quality of a host image. In recent years, there has been a significant development in gray-level image watermarking using fractal-based method. This paper presents a human visual system (HVS) based fractal watermarking method for color images. In the proposed method, a color pixel is considered as a 3-D vector inRGBspace. And a general form of 3 × 3 matrix is utilized as the scaling operator. Meanwhile, the luminance offset vector is substituted by the range block mean vector. Then an orthogonalization fractal color coding method is achieved to obtain very high image quality. We also show that the orthogonalization fractal color decoding is a mean vector-invariant iteration. So, the range block mean vector is a good place for hiding watermark. Furthermore, for consistency with the characteristics of the HVS, we carry out the embedding process in theCIE La*b*space and incorporate a just noticeable difference (JND) profile to ensure the watermark invisibility. Experimental results show that the proposed method has good robustness against various typical attacks, at the same time, with an imperceptible change in image quality.
Highlights
With the rapid development of internet, digital multimedia data such as image, audio, and video are readily reproduced and distributed with ease
In order to verify that the proposed algorithm described before increases the robustness of the watermarked images against attacks, a series of experiments has been conducted by using the attacks to the 512 × 512 color Lena, Peppers, and Barbara images, as shown in Figures 2(a), 2(d), and 2(g)
We have developed a fractal color image watermarking method and assessed its performance
Summary
With the rapid development of internet, digital multimedia data such as image, audio, and video are readily reproduced and distributed with ease. Many watermarking methods have been exploited for copyright protection due to the properties of digital media and the popularity of the internet. A watermark can be a random signal, a meaningful message, or a logo. It is viewed as an effective way to prevent user’s content from illegal distribution [1]. An encrypted watermark is inserted into an original image by using an embedding algorithm. When the watermark is to be extracted, the corresponding extraction algorithm will be implemented, usually with aid of a secret key and the original image. A good watermarking scheme should possess many important properties, for example, invisibility, robustness to various types of attacks, and accurate detection
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